Recently, in order to meet requests for reducing space, improving assembling work and improving control ability in automobiles, mechanical drive systems are changed to by-wire systems in which an actuator such as a motor or the like is used for electrical driving.
Patent Document 1 (JP-2006-336691-A) describes this kind of by-wire systems, in which a monitor control circuit (e.g., engine control circuit) is provided separately from a by-wire control circuit electrically controlling the actuator. The monitor control circuit monitors the by-wire system based on predetermined monitoring information. When the monitor control circuit identifies abnormality of the by-wire system, the control of the actuator by the by-wire control circuit is prohibited (e.g., a switch is turned off to cut off the power supply to the actuator).
Patent Document 1: JP-2006-336691-A
However, in the technology of Patent Document 1, since the control of the actuator by the by-wire control circuit is prohibited only when the monitor control circuit identifies abnormality based on predetermined monitoring information, the actuator is in a controllable state before the monitor control circuit identifies the abnormality. Therefore, it is difficult to sufficiently improve safety in case of system abnormality (e.g., generation of abnormal signals due to noise or source voltage lowering).